1. Field of the Invention
The present invention relates generally to agricultural seeders that produce open furrows in the soil into which seeds are placed, and more particularly to an improved furrow closing system that is depth-limited by linkages with a separate firming device so as to provide consistent closing of furrows in no-till conditions without the risk of disrupting seed placement.
2. Description of the Prior Art
Agricultural planting methods continue to improve in response to rapid worldwide adoption of no-till crop production techniques, in which the new crop""s seeds are placed directly into the previous crop""s stubble, also known as crop residues, and which consists of the stalks, straw and chaff left from the previous crop. No-till seeding differs greatly from seeding into a tilled seedbed. The soil conditions for no-till seeding will typically be more moist than those dried by tillage, due to the mulching effect of the crop residues remaining on the soil surface. Moist soils are more prone to compaction by implements traveling over or engaging the soil. No-till soils will also be more structurally stable than tilled soils, as the soil particles are xe2x80x9caggregatedxe2x80x9d or held together by old roots, fungi, and other organic material, which forms a matrix to hold the soil particles in place and naturally creates a highly porous but very resilient substrate. Agricultural seeders operating in no-till conditions are often built and operated so as to supply more down pressure (via springs and/or hydraulics) onto the furrow opening discs to aid in the slicing of old crop residues and to assist in the penetration of this more structured soil. The extra down pressure on the opener discs and depth-gauging wheels sometimes results in more compaction of the furrow sidewalls.
Especially in no-till, some difficulties are encountered when attempting to draw soil back into the furrow, which is desirable to protect the newly placed seeds from drying winds and sun, to protect from wildlife predation and damaging temperature fluctuations, to improve seedling uniformity of emergence and growth, and to improve seedling root establishment. In tilled soils, the most common method was to employ packing (xe2x80x9cpressxe2x80x9d) wheels rearward of the furrow openers; the packing wheels operated to both close the furrow and to do some amount of packing, since in the loose and dry tilled soils packing is desirable to assist the seed in drawing moisture from deeper in the soil. In no-till seeding, the wetter and more structured soils prevent packing wheels from performing adequately. The sidewall of the furrow formed in no-till seeding does not crumble easily like the sidewall in the tilled conditions, where the soil had previously been loosened and fluffed by tillage; accordingly, very high pressures are sometimes employed on the packing or closing wheels in an attempt to squeeze the furrow sidewalls back together. This typically results in poor seedling emergencexe2x80x94the seedling having great difficulty pushing itself through this dense layer of soilxe2x80x94as well as poor nodal or lateral root growth of emerged seedlings, since the compacted and xe2x80x9cslickenedxe2x80x9d sidewall resists root penetration.
Some improvements in no-till seeding have been made by separating the seed firming and furrow closing functions; this is only possible where the depth-gauging function is already accomplished independently of the packing or closing wheel, as in the configuration where depth-gauging wheels travel alongside the furrow opening discs. Seeds that have been placed into the soil by the furrow openers and seed-directing tube are then firmed into the bottom of the furrow by either a narrow rolling wheel (typified by U.S. Pat. No. 5,676,429 to Johnson, although similar wheels have long been used in the industry) or a sliding-type firmer (U.S. Pat. No. 5,425,318 issued to Keeton) which travels along the bottom of the furrow xe2x80x9cVxe2x80x9d and exerts a slight amount of pressure onto the seeds and surrounding soil. Since the closing wheel is now relieved of its seed firming function, the closing wheel may be comprised of a spoked or tined shape to more aggressively slice or fracture the sidewall of the furrow.
Several spoked closing wheels types and methods have been disclosed in the prior art, including, for example, U.S. Pat. No. 5,443,023 issued to Carroll, U.S. Pat. No. 5,497,717 issued to Martin, and U.S. Pat. No. 5,896,932 issued to Bruns et al., as well as improvements made in the angles and alignments of the spokes as they enter the soil (Applicant""s co-pending application Ser. No. 09/432,455). All of these spoked closing wheel arrangements regulate their depth by the shape and length of the spoke, the path of rotation of the spoke in relation to the furrow, as well as the weight of the wheel and its mounting bracket/arm and spring pressure exerted on the bracket/arm. The method described in the ""455 application further limits depth by the angle of the spoke as it enters the soil in conjunction with its close alignment to the furrow.
Many aspects of the field""s condition affect both the operating depth and furrow covering achieved by spoked closing wheels, such as changes in soil moisture level, amounts of stubble on the surface, soil texture, soil organic matter, soil structure, and amount of soil lifting or fluffing perpetrated by the opener disc or other devices. The operator must remain vigilant and continually adjust the down pressure on the closing wheels to achieve adequate furrow covering but yet not penetrate too far and disrupt seed placement. As a practical matter, this is extremely difficult to do as field conditions change frequently during the course of even a single pass with the seeding implement. While the method described in the ""455 application mitigates these problems to a significant degree, the invention described herein will allow spoked wheels to be built of heavier materials or operated even more aggressively without concern of disrupting seed placement; i.e., the current invention opens the door for previously impractical or undesirable angles and alignments for the spokes of closing wheels.
In the current state of agricultural seeder manufacturing and usage, some dichotomy has arisen between xe2x80x9cplantersxe2x80x9d and xe2x80x9cgrain drillsxe2x80x9d (or simply xe2x80x9cdrillsxe2x80x9d). The dichotomy is not particularly relevant to this application, except in the ease of describing the prior art in detail. For clarity, the term xe2x80x9cplanterxe2x80x9d commonly refers to seeders with the capability of singulating seeds for each opener unit""s placement, and typically with a relatively wide spacing between individual opener units (xe2x80x9copener unitxe2x80x9d refers to the entire seed placement apparatus for one furrow, including not only the furrow opening device, but also seed-directing tube, gauge wheel, firming and closing devices, linkages, etc.). Virtually all planters have parallel linkages to attach the opener unit to the toolbar, which results in no changes in the angle of operation of the opener unit as it engages the soil on undulating terrain. Planters almost universally utilize two furrow-opening discs on each opener unit, mounted immediately adjacent to each other and in contact with each other at their lower leading edge, but slightly away from each other toward their upper and rearward edges, which allows for a seed-directing tube between them. Planters typically employ depth-gauging wheels on the outside of each opening disc. Planters often have a radially mounted vertically pivoting bracket mounted rearward of the opening discs; the bracket holding the closing wheels inclined at 20xc2x0 to 24xc2x0 from the vertical (xe2x80x9ccamberxe2x80x9d) and 0xc2x0 from the direction of travel, and accommodating either smooth rubber wheels, beveled cast iron wheels, or any of the spoked wheels previously described.
Planters sometimes use a separate seed firming mechanism, such as a sliding-type firmer (the Keeton patent previously described) attached on or near the seed tube and projecting rearward of it (but ahead of the closing wheels), or a small-diameter (approximately 5xe2x80x3) xe2x80x9cseed-lockxe2x80x9d wheel which is vertically mounted to run along the bottom of the furrow xe2x80x9cVxe2x80x9d behind the seed tube but ahead of the closing wheels. The separate firming devices that operate within the furrow are especially important for no-till seeding due to the poor performance of the closing wheels in achieving seed-to-soil contact in the structured and more resilient soils found in no-till, and the complete inability of many spoked closing wheel designs to supply any seed firming.
The term xe2x80x9cgrain drillxe2x80x9d commonly refers to a seeder lacking the capability of seed singulation; instead the seed is metered volumetrically. Drills tend to have the opener units mounted to achieve narrow row spacing, although the openers may be mounted in a staggered pattern of two or more ranks on a single toolbar. Drills are manufactured employing a wide variety of furrow openers, including non-rolling openers referred to as xe2x80x9choe,xe2x80x9d xe2x80x9cknifexe2x80x9d or xe2x80x9csweepxe2x80x9d depending on the shape of the sliding shank component used, and both single- and double-disc openers. The sliding shank-type openers typically gauge their depth from packer or press wheels which are typically quite wide and operate rearward of the shank. Some disc-openers also gauge their depth from a press wheel, while other models use a gauge wheel alongside the opener much like the planter openers.
The disc-openers with gauge wheels alongside the opener create the opportunity for more precision in separated firming and closing functions. One popular drill with separate depth-gauging, seed firming, and furrow closing mechanisms is manufactured by Deere and Co., of Moline, Ill., and sold as the Model No. 750 and its derivatives, the 752, 1850, 1860, and 1560, and are described, for example, in U.S. Pat. No. 5,595,130 issued to Baugher. The 750-style opener unit is radially mounted to the drill""s frame, which has some limitations as will be described. The 750-style opener has a vertical firming wheel with a semi-pneumatic rubber tire about 1xe2x80x3 wide and 10xe2x80x3 in diameter, which is intended to roll along the bottom of the furrow xe2x80x9cVxe2x80x9d (although it is slightly too wide to do so if the sidewall is firm and structured), and which is mounted on an arm which radially pivots vertically from its attachment point on the opener, slightly above and rearward of the disc hub. The 750-type opener has a separate closing wheel which operates slightly to the side of the furrow and at angles designed to squeeze part of the sidewall back into the furrow, and is mounted on an arm which also pivots radially (vertically) from its attachment point slightly above the firming wheel arm""s attachment point; both the firming wheel arm and the closing wheel arm are independent of each other and attach directly to the opener subframe.
Another popular drill opener which is functionally similar to the 750-style is the SDX, marketed by Case-New Holland Global with U.S. headquarters at Racine, Wis. The SDX has a slightly narrower firming wheel than the 750-style opener, but otherwise is nearly identical in terms of the firming and closing wheel arrangement. The SDX is also radially attached to the drill frame.
Yet another drill opener with separate depth gauging and firming/closing functions is the Flexicoil Model F/SO opener marketed on a variety of toolbars. The F/SO combines the firming and closing functions in one solid rubber wheel adjustable in a small range of vertical and horizontal angles, approximately from 0xc2x0 to 10xc2x0 from vertical and 0xc2x0 to 10xc2x0 from direction of travel. The F/SO is attached to the toolbar via a parallel linkage, unlike the radial arrangements of the SDX and 750-style openers.
Hiniker Mfg. of Minnesota also produces a single-disc opener with separated depth gauging, seed firming, and furrow closing functions, where the firming is accomplished by a sliding-type firmer, and the closing is accomplished by a notched disc on a vertically pivoting radially mounted arm. This arrangement is described, for example, in U.S. Pat. No. 6,119,608 issued to Peterson et al. The Hiniker opener unit attaches to the toolbar via a parallel linkage.
On all of these planters and gauge-wheel type drills, the original closing wheels have often been replaced with spoked closing wheels to improve performance in structured no-till soils. The performance of such spoked closing wheels has varied considerably, depending on the exact design used, angles and alignment used, as well as soil conditions. Aggressiveness of the closing system has always been limited by the desire to avoid disrupting seed placement, there being no effective way of preventing the closing system from penetrating too far except by limiting the weight and down pressure exerted on the closing wheel, as well as the shape and length of the spokes on the wheel itself and the angles at which the spokes penetrate the soil. Furthermore, there has been some inadequacy of both the firming and closing wheels to track the furrow when seeding on the contour; this has been especially pronounced with firming wheels that taper to a very narrow edge.
The present invention provides an improved solution to the agronomic problems of furrow closure in no-till seeding, as previously discussed. By limiting the depth of the closing wheel as gauged by the firming wheel or other firming device running along the bottom of the furrow, a more aggressive closing system may be used, without the limitations on weight or down pressure in previous closing systems. The opener subframe on which the invention is attached is preferably mounted on a parallel linkage, rather than a radial pivot arm, to maintain a constant operating angle throughout its range of vertical movement. The firming wheel is also preferably attached to the opener subframe using a parallel linkage to maintain a constant operating angle throughout its range of vertical movement. Other mounting arrangements, such as a telescoping tube-within-a-tube assembly, can also be used to maintain the desired orientation.
The Applicant""s invention utilizes a large-diameter firming wheel with a narrow tapered edge to allow it to fit into the bottom of the furrow xe2x80x9cV.xe2x80x9d The firming wheel is rotatably attached to a stem, which is mounted on a parallel linkage rearward of the opener disc and seed directing tube; the parallel linkage may be downwardly biased by a spring or other arrangement for supplying some slight additional down pressure onto the firming wheel. The firming wheel""s parallel linkage is preferably mounted to a swivel assembly (e.g., a kingpin) that allows the linkage and firming wheel to articulate or swivel laterally a few degrees independent of the opener subframe to allow the firming wheel to better track the furrow when seeding along a contour.
Attached to the firming wheel stem, rearward of the firming wheel parallel linkage, is the closing wheel arm. The closing wheel arm is radially mounted to pivot vertically, to facilitate clearing the wheel should straw or stalks become lodged between the closing wheel and the firming wheel; the arm may be downwardly biased by a spring or similar mechanism. An adjustable stop limits the downward travel available to the closing wheel armxe2x80x94this is the essence of the invention, the control over the depth of the closing wheel accomplished by gauging from the firming wheel""s depth, which is also the depth of the seed. In this way, the closing wheel can be very aggressive without risk of it penetrating too far and disrupting seed placement.
The present invention may be configured with either one or two closing wheels per furrow, depending on the configuration of the opener discs, the crop seeded, and soil conditions. There may be other ways of attaching the closing wheel and firming wheel to achieve similar results, which will be obvious to those skilled in the art based on the teachings herein.
According to a broad aspect of the present invention, an opener unit for an agricultural seeder is provided, comprising: an opener subframe; a furrow opener mounted to the opener subframe for making an open furrow in soil; a seed directing device for directing seeds into the open furrow; a firming assembly having a support member attached to the opener subframe, and a firming device mounted to the support member and arranged to roll or slide along a bottom of the open furrow behind the seed directing device; and at least one closing wheel assembly having a closing wheel arm attached to the support member, and a closing wheel rotatably mounted to the closing wheel arm and arranged to close the open furrow behind the firming device.
According to another broad aspect of the present invention, a seed firming and furrow closing system for agricultural seeders is provided, comprising: a firming assembly support member adapted to be attached to an opener subframe; a firming device mounted to the support member and arranged to roll or slide along a bottom of an open furrow behind a seed directing device; a first closing wheel arm attached to the support member; and a first closing wheel rotatably mounted to the closing wheel arm and arranged to close an open furrow behind the firming device.
According to yet another broad aspect of the present invention, a method of seeding an agricultural crop is provided, comprising the steps of: creating an open furrow in soil; placing seeds into the furrow; moving a firming device along a bottom of the furrow; and closing the furrow using a spoked closing wheel mounted behind the firming device, the closing wheel being connected to the firming device such that an operating depth of the closing wheel is dependent upon and limited by a depth of the furrow in which the firming device is moving.